Syncthing replicates data between the two. ZFS auto snapshots prevent accidental or malicious data loss at each site. Various services are running on both machines. Plex, Wiki.js, OpenProject, etc. Most are run in docker, managed via systemd. The main machine is also used as a workstation as well as games. The storage arrays are ghetto special - USB 3 external disks, some WD Elements, some Seagate in enclosures. I even used to have a 1T, a 3T and a 4T disk in an LVM volume pretending to be an 8T disk in one of the ZFS pools. The next time I have to expand the storage I'll use second hand disks. The 5950X isn't boosting as high as it should be able to on a chipset with PB2, but I got all those cores on a B350 board. 😆 Config management is done with SaltStack.
I'll have to double check, but I came from a B450 board. It definitely allowed me to run my RAM at a higher XMP profile (4x 3200MHz), and it has way better IOMMU groups. Each PCIe device gets its own group, so they can all be passed to different VMs.